body {
    /* 初始化，取消内外边距 */
    margin: 0;
    padding: 0;
    /*  100%窗口高度 */
    height: 100vh;
    /* 渐变背景 */
    background: linear-gradient(200deg, #e3eeff, #f3e7e9);
}

.search-box {
    /* 绝对定位，水平居中垂直 */
    position: absolute;
    top: 50%;
    left: 50%;
    // 平移
    transform: translate(-50%, -50%);
    background-color: #2f3640;
    height: 40px;
    padding: 10px;
    border-radius: 40px;
    &:hover {
        .search-txt {
            width: 194px;
            padding: 0 6px 0 6px;
        }
        .search-btn {
            background-color: #fff;
        }
    }
    .search-txt {
        border: none;
        background: none;
        outline: none;
        float: left;
        padding: 0;
        color: #fff;
        font-size: 16px;
        line-height: 40px;
        width: 0;
        transition: 0.4s;
    }
    .search-btn {
        color: #e84118;
        float: right;
        width: 40px;
        height: 40px;
        border-radius: 50%;
        background-color: #2f3640;
        /* 弹性布局 水平垂直居中 */
        display: flex;
        justify-content: center;
        align-items: center;
        cursor: pointer;
        transition: 0.4s;
    }
}
